US 6920125

US patent 6920125, titled "IP adaptation layer on backhaul connection of cellular network," provides a method and system for optimizing the transmission of small, frequently delivered data packets in a cellular network's backhaul connection.

Here is a concise summary of US patent 6920125:

• Title: IP adaptation layer on backhaul connection of cellular network
• Original Assignee: Nortel Networks Ltd
• Current Assignee: [Apple Inc.](/litigations/by-plaintiff/Apple%20Inc.) (Note: The patent information indicates that the listed assignees may be inaccurate and Google has not performed a legal analysis as to the accuracy of the list.)
• Inventors: Geng Wu
• Filing Date: 2000-10-27
• Issue Date: 2005-07-19
• Abstract: The invention addresses the inefficiency of transmitting small-sized data packets (e.g., 10-20 bytes) with disproportionately large TCP/IP or UDP/IP headers (typically 40 bytes) over the backhaul connection between a Base Station Controller (BSC) and a Base Transceiver Subsystem (BTS) in a cellular network. To optimize bandwidth usage, it introduces an IP Adaptation Layer (IPAL) protocol. This protocol maps user connections, removes the large headers from these small, frequent information packets, and concatenates the data packets into an IPAL information packet. This IPAL packet is then tunneled over the backhaul connection, thereby reducing overhead and improving efficiency.
• Legal Status (as of 2026-05-29): Expired - Lifetime, expired on 2023-05-25.

Plain-Language Overview of Independent Claims:

• Independent Claim 1 (Method for communicating): This claim describes a method for efficient communication to a mobile device in a cellular network. It involves a Base Station Controller (BSC) receiving various user data packets. From these, it selects data packets that are small (20 bytes or less of data payload) and prepares an "adaptation layer information packet" from them. This adaptation layer packet is then tunneled from the BSC to a Base Transceiver Subsystem (BTS) over a dedicated backhaul connection.
• Independent Claim 15 (Method for communicating, with specific preparation): This claim details a method similar to Claim 1, focusing on the preparation step. After selecting small data packets (20 bytes or less), the adaptation layer information packet is prepared by concatenating multiple selected data packets into a single packet. An IP header is then added to this concatenated packet, which is subsequently tunneled from the BSC over the backhaul connection to the BTS.
• Independent Claim 27 (System for communicating): This claim defines a system for achieving the described efficient communication. The system includes a Base Station Controller (BSC) connected to a telecommunications network, and a Base Transceiver Subsystem (BTS) connected to the BSC via a dedicated backhaul. The BTS can communicate with mobile devices. The core feature is that the BSC is configured to receive user data packets, specifically select those with less than approximately 20 bytes of data payload, and then concatenate these selected small data packets to form an "adaptation layer information packet" for tunneling to the BTS.

CAFC 2026 Dockets:
A search of CAFC dockets for 2026 for patent number US6920125 did not yield any results. Given the patent's expired status as of May 25, 2023, it is highly improbable that there would be active litigation involving this patent in 2026.

As of April 26, 2026, a search for litigation involving US patent 6920125 did not yield any results on the specified platforms. Given that the patent's "Expired - Lifetime" status began on May 25, 2023, it is highly improbable that there would be active litigation concerning this patent at this time.

To conduct a comprehensive search for historical litigation prior to March 1, 2012, records would need to be requested from the National Archives and Records Administration, as the U.S. Court of Appeals for the Federal Circuit's online case records primarily cover cases filed on or after March 1, 2012. For cases filed after March 1, 2012, PACER (Public Access to Court Electronic Records) is the primary source for federal court case and docket information.

Proceedings overview

There are no AIA trial proceedings on file for US patent 6920125. This means all claims remain untested by the Patent Trial and Appeal Board (PTAB). For a defendant, this indicates that the patent's validity has not been challenged in an AIA trial, leaving all potential prior-art grounds available for future challenges, subject to the patent's expired status.

Strategic summary

As of 2026-05-29, all claims (1-40) of US patent 6920125 are UNTESTED by any AIA trial proceeding at the PTAB. The USPTO Open Data Portal API indicates no AIA trial proceedings, and a web search also did not surface any such proceedings.

Since there are no PTAB proceedings, the estoppel landscape under 35 U.S.C. § 315(e)(2) is not applicable. A defendant facing assertion of this patent would not be barred from raising any prior-art grounds, as no grounds have been raised or could have been reasonably raised in an IPR, PGR, or CBM.

The absence of PTAB activity is a notable signal. While not definitive, well-asserted patents often become targets for IPRs or other AIA trials, particularly if they are perceived as having validity weaknesses. The lack of such challenges suggests that either the patent has not been extensively asserted, or potential challengers have not identified strong grounds for an AIA trial, or perhaps the patent's expiration has rendered such challenges moot.

Recommended next steps

Given the complete absence of PTAB activity for US patent 6920125, there are no active proceedings, institution decisions, or Final Written Decisions to link to or quote.

The most important consideration is the patent's legal status: it expired on 2023-05-25. This means the patent can no longer be asserted for future infringement. Any demand letter or assertion related to this patent can only pertain to alleged past infringement that occurred before May 25, 2023.

If you are a defendant facing an assertion of US6920125, you should:

1. Confirm the expiration date and scope of alleged infringement: Verify that any alleged infringement indeed occurred before 2023-05-25.
2. Evaluate prior art for pre-expiration infringement: If alleged pre-expiration infringement is a concern, prior art grounds for invalidity (under 35 U.S.C. §§ 102 and 103) remain available for defense in district court litigation, as they have not been addressed by the PTAB. The absence of PTAB proceedings means that no claims have been "hardened" by surviving an IPR challenge.
3. Consider the economic viability: Given the patent's expiration, any potential damages would be limited to the period before May 25, 2023. This significantly limits the potential exposure and may make settlement or litigation less attractive for an asserting party.

The absence of PTAB activity means the patent's validity has not been scrutinized by the Board, which could be an advantage for a defendant needing to mount a validity challenge in court for past infringement.

Inventors

• Geng Wu: Inventor for Nortel Networks Ltd at the time of filing. The initial assignment on 2000-10-27 (Reel 011270/0314) records Geng Wu assigning their interest to Nortel Networks Limited.

Original Assignee

The original assignee was Nortel Networks Ltd.

• Primary line of business: Nortel Networks was a multinational telecommunications and data networking equipment manufacturer.
• Product embodiment: As a major telecommunications equipment provider, it is highly probable that Nortel Networks Ltd. incorporated backhaul optimization techniques, such as those described in US6920125, into their cellular network infrastructure products. The patent itself describes an "improved wireless communications system" and a "method for operation on the backhaul connection" (Description, Technical Field of the Invention).
• Current status: Nortel Networks filed for bankruptcy protection in 2009. Its assets, including its patent portfolio, were subsequently sold off, and the company has since dissolved.

Assignment timeline

• 2000-10-27 (executed) / recorded 2000-10-27 — Reel 011270/0314

  • Conveyance: Assignment
  • Assignor: WU, GENG
  • Assignee: NORTEL NETWORKS LIMITED
  • Correspondent: JOSEPH E. RUSZ, NORTEL NETWORKS CORPORATION, P.O. BOX 3511, STATION C, OTTAWA, ONTARIO K1Y 4H7, CANADA.
  • Context: Inventor assigned patent rights to their employer, the original assignee.

• 2001-07-05 (executed) / recorded 2002-02-19 — Reel 012636/0254

  • Conveyance: Assignment
  • Assignor: NORTEL NETWORKS LIMITED
  • Assignee: NORTEL NETWORKS LIMITED
  • Correspondent: TERRY W. PEACH, NORTEL NETWORKS CORPORATION, P.O. BOX 3511, STATION C, OTTAWA, ONTARIO K1Y 4H7, CANADA.
  • Context: Internal record update reflecting an address change for the original assignee.

• 2011-07-29 (executed) / recorded 2011-10-28 — Reel 027164/0356

  • Conveyance: Assignment
  • Assignor: NORTEL NETWORKS LIMITED
  • Assignee: ROCKSTAR BIDCO, LP
  • Correspondent: ROBERT E. HILL, FISH & RICHARDSON PC, P.O. BOX 1022, MINNEAPOLIS, MN 55440-1022. This correspondent firm also appears in subsequent assignments in this chain.
  • Context: Transfer of intellectual property assets from Nortel Networks Limited as part of its bankruptcy proceedings.

• 2012-05-11 (executed) / recorded 2012-07-27 — Reel 028661/0596

  • Conveyance: Assignment
  • Assignor: ROCKSTAR BIDCO, LP
  • Assignee: APPLE INC.
  • Correspondent: WONG, GLENN, FISH & RICHARDSON PC, P.O. BOX 1022, MINNEAPOLIS, MN 55440-1022. This correspondent firm also appeared in the previous assignment in this chain.
  • Context: Acquisition of patent rights by [Apple Inc.](/litigations/by-plaintiff/Apple%20Inc.) from Rockstar Bidco, LP.

• 2012-05-11 (executed) / recorded 2012-08-22 — Reel 028827/0291

  • Conveyance: Assignment (Corrective)
  • Assignor: ROCKSTAR BIDCO, LP
  • Assignee: APPLE INC.
  • Correspondent: WONG, GLENN, FISH & RICHARDSON PC, P.O. BOX 1022, MINNEAPOLIS, MN 55440-1022. This correspondent firm also appeared in previous assignments in this chain.
  • Context: Correction of a prior assignment record (Reel 028661/0596) to accurately reflect the application number.

Timeline diagram

timeline
    title Ownership of US 6920125
    2000 : Inventor Geng Wu to Nortel Networks
    2001 : Nortel address change
    2011 : Nortel to Rockstar Bidco LP (bankruptcy sale)
    2012 : Rockstar Bidco to Apple Inc
         : Corrective assignment to Apple

NPE / troll-pattern signals

1. Shell-entity transfer — Present. The transfer from Nortel Networks Limited to Rockstar Bidco, LP (Reel 027164/0356) and then from Rockstar Bidco, LP to Apple Inc. (Reel 028661/0596) involved Rockstar Bidco, LP, a consortium formed by operating companies specifically to acquire Nortel's patent portfolio. Rockstar Bidco itself functioned as a special purpose vehicle for intellectual property acquisition.
2. Known asserter in the chain — Not present. While Rockstar Bidco, LP was an aggregation vehicle, it is not listed as a typical NPE. The final assignee, Apple Inc., is a major operating company.
3. Repeat correspondent across the chain — Present. Fish & Richardson PC appears as the correspondent for the assignment from Nortel Networks Limited to Rockstar Bidco, LP (Reel 027164/0356) and for both assignments from Rockstar Bidco, LP to Apple Inc. (Reels 028661/0596 and 028827/0291).
4. Cascading transfers — Present. The transfer from Nortel to Rockstar Bidco was executed on 2011-07-29, followed by the transfer from Rockstar Bidco to Apple executed on 2012-05-11. This represents multiple assignments through chained entities within a period of less than 12 months.
5. Pre-litigation transfer — Unclear. The patent expired on 2023-05-25. Without information on any specific litigation dates related to this patent, it is not possible to determine if any transfers were strategically timed before an infringement suit.
6. Bankruptcy fire-sale — Present. The transfer from Nortel Networks Limited to Rockstar Bidco, LP (Reel 027164/0356) was a direct result of Nortel Networks' bankruptcy proceedings.
7. Privateering — Not present. The patent ultimately transferred to Apple Inc., an operating company. There is no indication of Apple using an NPE to assert this specific patent on its behalf.
8. Defensive aggregator (anti-NPE) — Not present. The chain terminates with Apple Inc., an operating company, not a defensive aggregator.

Verdict

Operating-company assertion. Although the patent was part of a bankruptcy fire-sale from Nortel Networks Limited to Rockstar Bidco, LP (Reel 027164/0356) and involved an intermediate aggregation entity, Rockstar Bidco, LP, the ultimate assignee is Apple Inc. (Reel 028661/0596), a large operating company. This indicates that the patent was acquired by an operating company, likely for strategic competitive reasons (defensive or offensive), rather than for assertion by a non-practicing entity.

Link to USPTO Assignment Center search for US6920125## Inventors

• Geng Wu: Inventor for Nortel Networks Ltd at the time of filing. The initial assignment on 2000-10-27 (Reel 011270/0314) records Geng Wu assigning their interest to Nortel Networks Limited.

Original assignee

The original assignee was Nortel Networks Ltd.

• Primary line of business: Nortel Networks was a Canadian multinational telecommunications and data networking equipment manufacturer. They supplied networking products and solutions, including hardware, software, and services, to service providers and enterprise customers worldwide. They played a significant role in the development of digital switching and fiber optic transmission systems.
• Product embodiment: As a major telecommunications equipment provider, it is highly probable that Nortel Networks Ltd. incorporated backhaul optimization techniques, such as those described in US6920125, into their cellular network infrastructure products. The patent itself describes an "improved wireless communications system" and a "method for operation on the backhaul connection" (Description, Technical Field of the Invention). Nortel was known for its contributions to wireless infrastructure and telephonic (voice) equipment.
• Current status: Nortel Networks filed for bankruptcy protection in January 2009 in Canada and the United States, and in the United Kingdom. Its assets, including its patent portfolio, were subsequently sold off to various buyers, and the company has since dissolved and ceased operations. The bankruptcy case was the largest in Canadian history.

Assignment timeline

• 2000-10-27 (executed) / recorded 2000-10-27 — Reel 011270/0314

  • Conveyance: Assignment
  • Assignor: WU, GENG
  • Assignee: NORTEL NETWORKS LIMITED
  • Correspondent: JOSEPH E. RUSZ, NORTEL NETWORKS CORPORATION, P.O. BOX 3511, STATION C, OTTAWA, ONTARIO K1Y 4H7, CANADA.
  • Context: Inventor assigned patent rights to their employer, the original assignee.

• 2001-07-05 (executed) / recorded 2002-02-19 — Reel 012636/0254

  • Conveyance: Assignment (Address Change)
  • Assignor: NORTEL NETWORKS LIMITED
  • Assignee: NORTEL NETWORKS LIMITED
  • Correspondent: TERRY W. PEACH, NORTEL NETWORKS CORPORATION, P.O. BOX 3511, STATION C, OTTAWA, ONTARIO K1Y 4H7, CANADA.
  • Context: Internal record update reflecting an address change for the original assignee.

• 2011-07-29 (executed) / recorded 2011-10-28 — Reel 027164/0356

  • Conveyance: Assignment
  • Assignor: NORTEL NETWORKS LIMITED
  • Assignee: ROCKSTAR BIDCO, LP
  • Correspondent: ROBERT E. HILL, FISH & RICHARDSON PC, P.O. BOX 1022, MINNEAPOLIS, MN 55440-1022. This correspondent firm, Fish & Richardson PC, appears in subsequent assignments in this chain.
  • Context: Transfer of intellectual property assets from Nortel Networks Limited as part of its bankruptcy proceedings.

• 2012-05-11 (executed) / recorded 2012-07-27 — Reel 028661/0596

  • Conveyance: Assignment
  • Assignor: ROCKSTAR BIDCO, LP
  • Assignee: APPLE INC.
  • Correspondent: WONG, GLENN, FISH & RICHARDSON PC, P.O. BOX 1022, MINNEAPOLIS, MN 55440-1022. This correspondent firm, Fish & Richardson PC, also appeared in the previous assignment in this chain.
  • Context: Acquisition of patent rights by Apple Inc. from Rockstar Bidco, LP.

• 2012-05-11 (executed) / recorded 2012-08-22 — Reel 028827/0291

  • Conveyance: Assignment (Corrective)
  • Assignor: ROCKSTAR BIDCO, LP
  • Assignee: APPLE INC.
  • Correspondent: WONG, GLENN, FISH & RICHARDSON PC, P.O. BOX 1022, MINNEAPOLIS, MN 55440-1022. This correspondent firm, Fish & Richardson PC, also appeared in previous assignments in this chain.
  • Context: Correction of a prior assignment record (Reel 028661/0596) to accurately reflect the application number.

Timeline diagram

timeline
    title Ownership of US 6920125
    2000 : Inventor Geng Wu to Nortel Networks
    2001 : Nortel address change
    2011 : Nortel to Rockstar Bidco LP (bankruptcy sale)
    2012 : Rockstar Bidco to Apple Inc
         : Corrective assignment to Apple

NPE / troll-pattern signals

1. Shell-entity transfer — Present. The transfer from Nortel Networks Limited to Rockstar Bidco, LP (Reel 027164/0356) involved Rockstar Bidco, LP, which was a consortium formed by operating companies (Apple, BlackBerry, Ericsson, Microsoft, and Sony) specifically to acquire Nortel's patent portfolio during its bankruptcy. Rockstar Consortium, originally named Rockstar Bidco, is described as a patent holding non-practicing entity (NPE) and a "patent aggression company" that examined products for infringement and sought licensing deals.
2. Known asserter in the chain — Present. Rockstar Bidco, LP (later Rockstar Consortium) is widely recognized as a patent holding and assertion entity. It was listed in 2012 as one of the "8 most fearsome patent trolls in industry" by Business Insider, and Wired magazine referred to it as a "straight-up patent troll". Rockstar initiated legal actions against numerous companies, including Google, Huawei, and Samsung, for infringement.
3. Repeat correspondent across the chain — Present. Fish & Richardson PC appears as the correspondent for the assignment from Nortel Networks Limited to Rockstar Bidco, LP (ROBERT E. HILL, Reel 027164/0356) and for both assignments from Rockstar Bidco, LP to Apple Inc. (WONG, GLENN, Reels 028661/0596 and 028827/0291).
4. Cascading transfers — Present. The transfer from Nortel to Rockstar Bidco was executed on 2011-07-29, and then from Rockstar Bidco to Apple on 2012-05-11. This represents two consecutive assignments through chained entities within a period of less than 12 months.
5. Pre-litigation transfer — Unclear. The patent expired on 2023-05-25. While Rockstar Consortium did engage in extensive litigation related to the Nortel patents, without specific dates for litigation involving this particular patent (US6920125), it is not possible to definitively state if these transfers were pre-litigation.
6. Bankruptcy fire-sale — Present. The transfer from Nortel Networks Limited to Rockstar Bidco, LP (Reel 027164/0356) was explicitly part of the Nortel Networks bankruptcy asset sale, where Rockstar Bidco submitted the winning US$4.5 billion bid for the patent portfolio.
7. Privateering — Not present. While Rockstar Consortium was formed by operating companies, and engaged in patent monetization on their behalf, the chain for this specific patent ultimately terminates with Apple Inc. as the direct assignee, rather than remaining with Rockstar for assertion. This suggests a direct acquisition by an operating company, though it originated from an aggregation entity with NPE characteristics.
8. Defensive aggregator (anti-NPE) — Not present. The chain terminates with Apple Inc., an operating company, not a defensive aggregator. Although Rockstar later sold 4000 of its patents to RPX Corporation (a defensive patent aggregator) in December 2014, this specific patent (US6920125) was assigned to Apple Inc. in 2012.

Verdict

NPE — moderate confidence. Although the patent's ultimate assignee is Apple Inc., a major operating company, the presence of Rockstar Bidco, LP in the chain (Reel 027164/0356 and Reel 028661/0596) is a strong NPE signal. Rockstar Bidco was a consortium explicitly described as a patent holding non-practicing entity (NPE) that engaged in patent monetization and litigation against numerous companies. The patent was acquired via a bankruptcy fire-sale (Reel 027164/0356) and went through Rockstar Bidco before reaching Apple, which aligns with NPE aggregation patterns even if the final destination is an operating company for this specific patent.

USPTO Assignment Center search for US6920125: https://assignmentcenter.uspto.gov/#!/assignment-result?id=7901594

The USPTO Patent Public Search tool can be used to search for patent numbers. To search for a utility patent with six, seven, or eight digits, the number should be entered without commas or spaces, omitting leading zeros. For example, a 6-digit patent number like '123456' should be entered as '0123456' to make it 7 digits.

Regarding US patent 6920125, the following prior art was cited by the examiner:

• US6049543A:
  • Full Citation: US6049543A, Motorola, Inc., "Transcoder for use in an ATM-based communications system"
  • Publication Date: 2000-04-11
  • Filing Date: 1996-12-27
  • Brief Description: This patent describes a transcoder for an ATM-based communication system that converts speech from a mobile station into ATM cells. It aggregates multiple voice calls onto a single ATM virtual circuit to improve bandwidth utilization.
  • Potential Anticipation (35 U.S.C. § 102): US6049543A potentially anticipates claims related to aggregating or concatenating data packets for multiple users and transmitting them over a backhaul connection to improve efficiency. Specifically, elements of claims 1, 10, 15, and 36, which describe concatenating multiple data packets into an adaptation layer information packet for tunneling or transmitting over the backhaul connection, may be implicated.
• US6230012B1:
  • Full Citation: US6230012B1, Qualcomm Incorporated, "IP mobility support using proxy mobile node registration"
  • Publication Date: 2001-05-08
  • Filing Date: 1998-08-07
  • Brief Description: This patent details a method for providing IP mobility support using proxy mobile node registration, allowing mobile nodes to maintain connectivity while moving between different networks. It discusses tunneling techniques in the context of mobile IP.
  • Potential Anticipation (35 U.S.C. § 102): US6230012B1 potentially anticipates claims relating to tunneling information packets, particularly claims 1, 11, 15, and 37, which describe tunneling the adaptation layer information packet from the base station controller unit through the backhaul connection or adding an IP header to the adaptation layer information packet for tunneling.
• US6233458B1:
  • Full Citation: US6233458B1, Nokia Telecommunications Oy, "Re-routing procedure"
  • Publication Date: 2001-05-15
  • Filing Date: 1997-06-24
  • Brief Description: This patent focuses on a re-routing procedure in a cellular network, particularly for optimizing data transfer paths. While not explicitly about header compression or concatenation, it addresses efficient data handling in a mobile environment.
  • Potential Anticipation (35 U.S.C. § 102): Given its general focus on efficient data transfer paths in cellular networks, US6233458B1 might broadly relate to the underlying problem addressed by US6920125, but it doesn't appear to directly disclose the specific solutions of header reduction or concatenation. Thus, direct anticipation of specific claims regarding the IP Adaptation Layer is less likely, but it could be considered for broader concepts of optimizing communication in cellular networks.
• US6396828B1:
  • Full Citation: US6396828B1, Telefonaktiebolaget Lm Ericsson (Publ), "Arrangement system and method relating to data network access"
  • Publication Date: 2002-05-28
  • Filing Date: 1997-03-13
  • Brief Description: This patent describes a system and method for accessing a data network, particularly focusing on handling data connections and resource allocation. It addresses aspects of data communication efficiency in mobile networks.
  • Potential Anticipation (35 U.S.C. § 102): Similar to US6233458B1, this patent addresses general aspects of data communication efficiency and resource allocation in mobile networks. Direct anticipation of the specific IPAL protocol, header elimination, or data concatenation features of US6920125 is unlikely.
• US6701361B1:
  • Full Citation: US6701361B1, Intermec Ip Corp., "Enhanced mobility and address resolution in a wireless premises based network"
  • Publication Date: 2004-03-02
  • Filing Date: 1996-08-22
  • Brief Description: This patent describes methods for enhanced mobility and address resolution in wireless networks, enabling mobile devices to move seamlessly.
  • Potential Anticipation (35 U.S.C. § 102): This patent focuses on mobility and address resolution, which are different technical problems than the specific bandwidth optimization through header reduction and data concatenation taught by US6920125. Therefore, direct anticipation of claims in US6920125 is unlikely.
• US6751207B1:
  • Full Citation: US6751207B1, Cellco Partnership, "Tunnelling voice over the internet protocol in a cellular network"
  • Publication Date: 2004-06-15
  • Filing Date: 1999-07-27
  • Brief Description: This patent describes tunneling voice over IP (VoIP) in a cellular network. It deals with transmitting voice communications as IP packets and could involve mechanisms for efficient transport.
  • Potential Anticipation (35 U.S.C. § 102): US6751207B1 specifically mentions "tunneling voice over the internet protocol in a cellular network", which directly relates to the concept of tunneling voice-over-IP (VoIP) users that are a focus of US6920125 for small, frequently transmitted data packets. This patent could potentially anticipate claims 1, 3, 4, 11, 15, 17, 18, and 37, which refer to tunneling adaptation layer information packets and handling frequently transmitted data packets like those for VoIP users.

Obviousness Analysis under 35 U.S.C. § 103

A patent claim is considered obvious if, at the time of the invention, a person of ordinary skill in the art would have been motivated to combine prior art teachings or modify prior art to arrive at the claimed invention with a reasonable expectation of success. This requires clear, fact-based reasoning and guards against hindsight bias. Motivation to combine prior art can stem from the knowledge of those skilled in the art, from the prior art references themselves, or from the nature of the problem to be solved.

Identifying Potential Combinations of Prior Art

To assess the obviousness of US patent 6920125, we will examine its cited prior art references. The patent itself lists both patent and non-patent citations.

Patent Citations:

• US6049543A (Motorola, Inc.): "Transcoder for use in an ATM-based communications system" [cite: The "Patent Citations" section of US6920125B1]
• US6230012B1 (Qualcomm Incorporated): "IP mobility support using proxy mobile node registration" [cite: The "Patent Citations" section of US6920125B1]
• US6233458B1 (Nokia Telecommunications Oy): "Re-routing procedure" [cite: The "Patent Citations" section of US6920125B1]
• US6396828B1 (Telefonaktiebolaget Lm Ericsson (Publ)): "Arrangement system and method relating to data network access" [cite: The "Patent Citations" section of US6920125B1]
• US6701361B1 (Intermec Ip Corp.): "Enhanced mobility and address resolution in a wireless premises based network" [cite: The "Patent Citations" section of US6920125B1]
• US6751207B1 (Cellco Partnership): "Tunnelling voice over the internet protocol in a cellular network" [cite: The "Patent Citations" section of US6920125B1]

Non-Patent Citations:

• El-Khatib, K. and G. Bochman, "Multiplexing Scheme for RTP Flows Between Access Routers," IETF, Dec. 24, 1999. [cite: The "Non-Patent Citations" section of US6920125B1]
• Hoshi, Tohru, "Voice Stream Multiplexing Between IP Telephony Gateways," IEICE Trans, Apr. 1999. [cite: The "Non-Patent Citations" section of US6920125B1]
• La Porta, Thomas F., Luca Salgarelli and Gerald T Foster; "Mobile IP and Wide Area Wireless Data; " 1998; IEEE Internet Computing. [cite: The "Non-Patent Citations" section of US6920125B1]
• Perkins, C.; "RFC 2002: IP Mobility Support; " Oct. 1996; Network Working Group. [cite: The "Non-Patent Citations" section of US6920125B1]
• Perkins, C.; "RFC 2003: IP Encapsulation within IP; " Oct. 1996; Network Working Group. [cite: The "Non-Patent Citations" section of US6920125B1]
• Perkins, Charles E.; "Tutorial: Mobile Networking Through Mobile IP; " Jan. 1998; IEEE Internet Computing. [cite: The "Non-Patent Citations" section of US6920125B1]
• Simpson, W.; "RFC 1853: IP in IP Tunneling; " Oct. 1995; Network Working Group. [cite: The "Non-Patent Citations" section of US6920125B1]
• Subbiah, B. and S. Sengodan, "User Multiplexing in RTP Payload Between IP Telephony Gateways," IETF, Feb. 21, 1999. [cite: The "Non-Patent Citations" section of US6920125B1]
• Subbiah, Baranitharn, Method and Apparatus for Providing User Multiplexing in a Real-Time Protocol, International Publication No. WO 00/11849, Mar. 2, 2000. [cite: The "Non-Patent Citations" section of US6920125B1]

Motivation to Combine

The central problem addressed by US6920125 is the inefficient use of bandwidth on the backhaul connection between a BSC and BTS due to large TCP/IP or UDP/IP headers on small, frequently transmitted data packets, such as those for voice communications (e.g., VoIP). [cite: The "Abstract" section of US6920125B1] The solution involves an IP Adaptation Layer (IPAL) to map user connections, eliminate large headers, concatenate small data packets, and tunnel them over the backhaul. [cite: The "Abstract" section of US6920125B1]

A person having ordinary skill in the art (POSITA) at the time of the invention (2000-10-27) would have been keenly aware of the need to optimize bandwidth in cellular networks, especially for real-time applications like voice. The listed prior art clearly demonstrates existing knowledge of IP mobility, tunneling, and multiplexing of real-time protocol (RTP) flows, as well as ATM-based communication systems.

The motivation to combine these concepts to solve the problem of excessive overhead for small packets on backhaul connections would have been evident from "the nature of the problem to be solved" and "any need or problem known in the field of endeavor at the time of invention and addressed by the patent".

Here's an analysis of potential combinations:

Combination 1: US6751207B1 + El-Khatib et al. (1999) or Hoshi (1999) or Subbiah et al. (1999) or WO 00/11849

• US6751207B1 (Cellco Partnership): "Tunnelling voice over the internet protocol in a cellular network" This patent explicitly teaches tunneling voice over IP in a cellular network. [cite: The "Patent Citations" section of US6920125B1] This directly addresses the context and the type of data (voice) that US6920125 seeks to optimize.
• El-Khatib et al. (1999): "Multiplexing Scheme for RTP Flows Between Access Routers" / Hoshi (1999): "Voice Stream Multiplexing Between IP Telephony Gateways" / Subbiah et al. (1999): "User Multiplexing in RTP Payload Between IP Telephony Gateways" / WO 00/11849 (Subbiah, Baranitharn): "Method and Apparatus for Providing User Multiplexing in a Real-Time Protocol" These non-patent citations all describe methods for multiplexing real-time protocol (RTP) flows or voice streams. Multiplexing, in this context, inherently aims to combine smaller data streams for more efficient transmission. [cite: The "Non-Patent Citations" section of US6920125B1]

Motivation to Combine: A POSITA, seeking to optimize bandwidth for voice over IP in a cellular network (as taught by US6751207B1), would be motivated to combine this tunneling approach with known methods for multiplexing real-time voice streams (as taught by El-Khatib et al., Hoshi, Subbiah et al., or WO 00/11849). The problem of disproportionately large headers on small voice packets, as described in US6920125, would provide a strong motivation to use multiplexing to aggregate these small packets and thereby reduce the effective header overhead per data unit. The concept of using an adaptation layer to perform such a function would be a natural engineering choice to interface between the higher-layer RTP/IP and the lower-layer cellular backhaul.

Combination 2: US6049543A + Perkins (RFC 2003) or Simpson (RFC 1853)

• US6049543A (Motorola, Inc.): "Transcoder for use in an ATM-based communications system" This patent describes a transcoder in an ATM-based communication system. US6920125 explicitly states that its IPAL protocol is compatible with "ATM-based BSC 219 and BTS 250 units." [cite: The "Definitions" section of US6920125B1] This indicates that the environment of the invention includes ATM technology.
• Perkins, C.; "RFC 2003: IP Encapsulation within IP" / Simpson, W.; "RFC 1853: IP in IP Tunneling" These RFCs describe IP encapsulation within IP, commonly known as IP-in-IP tunneling. [cite: The "Non-Patent Citations" section of US6920125B1] Tunneling is a core mechanism in US6920125 for transmitting the aggregated IPAL packets.

Motivation to Combine: Given that US6920125 operates in an ATM-based cellular environment, a POSITA would be motivated to integrate the IP-in-IP tunneling techniques (from RFC 2003 or RFC 1853) into an ATM-based communication system (as described in US6049543A). The problem of reducing overhead for smaller IP packets within such a system would drive the adaptation of tunneling, potentially through an adaptation layer, to efficiently transport these packets over the existing ATM backhaul. The patent acknowledges the compatibility with ATM equipment, suggesting that adapting IP tunneling for an ATM infrastructure would be a known or obvious consideration for improving data transfer efficiency.

Combination 3: US6230012B1 or Perkins (RFC 2002) or La Porta et al. (1998) or Perkins (1998 Tutorial) + The general problem of backhaul efficiency

• US6230012B1 (Qualcomm Incorporated): "IP mobility support using proxy mobile node registration" / Perkins, C.; "RFC 2002: IP Mobility Support" / La Porta et al. (1998): "Mobile IP and Wide Area Wireless Data" / Perkins, Charles E.; "Tutorial: Mobile Networking Through Mobile IP" These references all deal with aspects of Mobile IP, which is concerned with maintaining IP connectivity for mobile nodes as they change their point of attachment to the Internet. While not directly about header compression, they highlight the context of IP communication to mobile nodes in wireless networks. [cite: The "Non-Patent Citations" section of US6920125B1]
• The general problem of backhaul efficiency: The background of US6920125 clearly articulates the problem of inefficient bandwidth usage on the backhaul due to large headers on small, frequent packets. [cite: The "Description" section of US6920125B1]

Motivation to Combine: A POSITA working with Mobile IP solutions (as described in US6230012B1, RFC 2002, La Porta et al., or Perkins's tutorial) would be acutely aware of the challenges of transmitting data to mobile nodes, particularly over constrained wireless and backhaul links. The acknowledged problem of disproportionately large headers for small packets (such as those arising from VoIP, a common mobile application) would provide a strong motivation to apply header reduction and packet aggregation techniques to optimize the backhaul connection. The "nature of the problem" of backhaul inefficiency, especially for mobile IP traffic, would motivate a skilled artisan to implement an adaptation layer that performs header stripping and concatenation to make the mobile IP traffic more efficient over the backhaul.

Conclusion on Obviousness

The core inventive step of US6920125 lies in the selective application of an IP Adaptation Layer (IPAL) to specifically target small, frequently transmitted data packets by removing their large TCP/IP/UDP/IP headers, concatenating them, and then tunneling them over the backhaul. [cite: The "Abstract" section of US66920125B1]

While no single prior art reference explicitly describes the entire IPAL protocol as claimed, the combination of existing knowledge would render the claimed invention obvious. Specifically:

• The concept of tunneling IP traffic was well-established (RFC 1853, RFC 2003). [cite: The "Non-Patent Citations" section of US6920125B1]
• The need for multiplexing and aggregating real-time flows, particularly voice, to improve efficiency was known (El-Khatib et al., Hoshi, Subbiah et al., WO 00/11849). [cite: The "Non-Patent Citations" section of US6920125B1]
• The general problem of header overhead impacting bandwidth efficiency, especially for small packets, was a recognized challenge in network communications, including cellular backhaul. [cite: The "Description" section of US6920125B1]
• The use of adaptation layers in ATM-based systems to handle different data types was a known architectural approach (US6049543A implicitly, and US6920125 itself notes compatibility with ATM equipment). [cite: The "Definitions" section of US6920125B1]

A POSITA, motivated by the clear need to improve backhaul efficiency for frequently transmitted small packets (such as voice/VoIP traffic to mobile nodes), would have found it obvious to combine existing tunneling mechanisms with multiplexing techniques within an adaptation layer structure, particularly in an ATM-compatible cellular network environment. The selective application of this adaptation layer to specific types of traffic (small, frequent packets) would be a matter of design choice to maximize efficiency where it is most needed, without burdening other traffic.

Therefore, the claims of US patent 6920125, particularly independent claims 1, 15, and 27, would likely be considered obvious under 35 U.S.C. § 103 given the cited prior art and the recognized problems in the field.